The move to 18-inch tyres comes as part of F1's major rules overhaul for next year, which is aimed at having drastically different-looking cars that produce better racing compared to the current machines.
The F1-supporting Formula 2 series will run 18-inch tyres in 2020, which will provide data for Pirelli's '21 development programme this year.
The initial running for that development took place in the later stages of 2019.
When asked what would happen if the teams raised issues with the 2021 rubber, which happened last year and led to Pirelli abandoning its plan to introduce new tyres for '20, Isola – Pirelli's motorsport boss – told Motorsport.com: "Luckily, we already ran three test sessions in '19.
"And the first feedback from 18-inch tyres is quite good. So, I'm not expecting to have any kind of surprise this year.
"Obviously, the car will be different [in 2021]. The car is designed on 18-inch tyres, so in '21, we will have a new product. No chance to go back to 13-inch tyres.
"But I'm positive because especially the first session [when] we were in Paul Ricard with Renault [last September] we did 213 laps in two days.
"[With] a mule car, the first time [the team is] running a new car, the first time we are running the 18-inch tyre, new rims – new everything – you expect to have an issue and maybe usually have to stop for half a day or maybe more.
"[But] we had no issues at all. We did all our run plan in the two days. We're ran more than 1000km. So, it was quite a productive two-day test."
Isola said he is "very positive for 2021", regarding the potential for the new rules to improve racing.
"If the new aero package is working as predicted, with a lot less influence in downforce for the car that is following, it will change the situation a lot," he continued.
"[This is] because the current cars, when you follow the car in front of you, you lose up to 50% of downforce."